It is a general object of this invention to provide vehicular transportation capable of moving varied loads at varied speeds and under varied conditions, utilizing a prime mover having capabilities that require mechanical advantage, particularly when human powers are relied upon. Although the concepts herein disclosed are applicable to engine or motor powered vehicles and/or like devices, it is the human powered vehicle and/or device such as a bicycle in which this invention is advantageously embodied as hereinafter disclosed. Working pressure available from human power is substantial while continued muscular effort through the movement of human limbs is limited, and therefore efficient mechanical advantage is much to be desired, and it is to these ends that I have provided this improved and cooperatively related vehicle, transmission and braking.
Referring to the motivating power necessary to accelerate and to propel bicycles and the like, especially human powered vehicles, a multi-speed transmission is commonly employed, but limited to certain spaced gear ratios. Derailleur chain and sprocket gearing is commonly employed, and there are geared hubs, for implementing speed ratio changes between the foot pedal operated crank and the supporting drive wheel. The commonly accepted type of gear changer is the Derailleur type, with its speed ratio limitations and complexities which not only encumber the vehicle but which are vulnerable to damage. Therefore, it is an object of this invention to eliminate gear ratio limitations and to provide infinitely variable gear ratios within the range required. With the present invention, a variable ratio transmission is provided for changing the angular velocity from an input shaft to an output shaft; and in the particular case illustrated, to increase angular velocity from a bicycle crank shaft to a drive sprocket that rotates a drive wheel (the rear wheel).
Variable ratio transmissions of the prior art have not been positive, and in one way or another rely upon frictional engagement between the drive and driven members; reference being made to cone or V-belt pulley drives, disc and roller drives. Also, variable ratio transmissions exist in the form of both hydraulic and electric apparatus wherein current flow is controlling, but not absolutely positive in every application. On the contrary, meshed gear engagement is positive and it is therefore an object of this invention to provide positive in-mesh infinitely variable ratio transmission of rotative power having the advantages of direct and positive gear engagement between an input shaft and an output shaft. With the present invention, there is a constant mesh ratio changer and variable speed feedback to an element thereof adding to or subtracting from the output velocity, and in the preferred embodiment there are first and second stages of gearing and there is a variable speed feedback into one stage to add or substract angular velocity as may be required. A feature of the transmission is the feedback through non-reversible gearing which substantially reduces the torque requirement of the infinitely variable speed control means that governs the input-output speed ratio.
Transmissions involving gears and controls therefor are most often weighty and space consuming, it being an object of this invention to provide a variable ratio transmission of the character thus far referred to that is small and compact, and consequently of relatively light weight. The bicycle, for which the embodiment herein disclosed is designed, is a light weight competition cycle, in which case the input torque on the crank shaft is quite high. Therefore, it is also an object to provide a durable gearing that will withstand any and all mechanical pressures likely to be imposed thereon. In practice, the first and second gearing stages are of the planetary type with multiple pinions having wide faced toothed engagement, while the speed regulating control means includes a non-reversible worm and wheel feedback drive into the second stage gearing operating at lower torque value than the first stage gearing. Anti-friction bearings are used exclusively in the journaling of all torque transmitting and/or higher velocity elements.
The independent controllability of prior art bicycle transmissions and braking has involved separate manual controls, the former requiring selective positioning and the latter requiring forceful actuation. It is an object of this invention to combine the independent controllability of these two control functions into one control means by which both selective positioning and forceful actuation are manually applied. As will be described, the controlling means comprises a lever having distinct modes of actuation, one whereby it is rotatively positioned to effect selectivity of the variable output ratio of the transmission hereinabove referred to, and one whereby it is forcibly displaced to effect actuation of the brake.
The usual hanger assembly of the conventional bicycle is replaced in the present invention, it being an object to provide a frame adapted to accept the transmission of the character hereinabove referred to. In practice, the said transmission and its control means are combined in a casing adapted to be disassembled for accessibility, and for removal and replacement.